Wound exudate can be described as the liquid produced from chronic wounds, fistula, or acute wounds once haemostasis has been achieved. For centuries, the production of exudate was regarded as inevitable with certain types of wound, and inconsequential with respect to wound healing.
More recently, considerable attention has been given to the development of wound dressings that prevent the accumulation of large volumes of fluid within a wound, and also prevent the fluid from spreading over the surrounding healthy tissue. This is because excessive wound exudate can cause maceration of the peri-wound skin, which in turn can lead to infection. One technique known in the art is the application of suction through the wound dressing, to create and maintain negative pressure at the wound site. Negative pressure means pressure below surrounding atmospheric pressure. Such a technique is referred to in the art as Topical Negative Pressure (TNP). This is believed by some researchers to aid drainage of wound exudate away from the wound bed, reduce infection rates, and increase localized blood flow.
Maintaining negative pressure at the wound site may create some practical problems:
(i) The negative pressure may be able to draw tissue growth into the pores of a foam piece inside the wound dressing. This can result in discomfort to the patient during use of the device, especially when the dressing is removed or replaced. Removal or replacement of the dressing may also cause damage to that newly grown tissue.
(ii) The wound is vulnerable to drying out of wound exudate. This condition may be undesirable because exudate is believed to contain a complex mixture of bioactive molecules that have both positive and negative effects. While removal of excess exudate is desirable, removal of all exudate may hinder rather than aid wound healing. Proper use of the wound dressing may depend to a large extent on the expertise of medical staff in assessing the rate of production of wound exudate at the wound site, and adjusting the negative pressure accordingly. If frequent removal of the dressing is required to assess the state of the wound, this merely exacerbates discomfort caused by drawback (i) above.
Some of the potential drawbacks may be partly mitigated by the use of hydro-fiber as described in U.S. Patent Publication No. 2006/0100594.
The present invention has been devised bearing potential issues in mind.